UNDERSTANDING VISUAL FIELD TESTING Definitions Indications For

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Definitions

 Visual Field:  The portion of space which is visible when gaze is fixed in one direction

 Perimetry:  The measurement of the extent and sensitivity of the visual field UNDERSTANDING VISUAL FIELD TESTING

Caroline B. Pate, OD, FAAO Associate Professor, UAB School of Optometry, Birmingham, AL

Indications for Perimetry Indications for Perimetry

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 History  Examination  General medical problems  Unexplained reduction in  Neurological problems best corrected visual  Ophthalmic problems acuity  Potentially toxic medications  Defect noted on confrontation fields  Abnormal pupils or EOM’s  Proptosis  Elevated intraocular pressure

Indications for Perimetry Purposes of Perimetry

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“Funny looking  Retinal or Choroidal  Detection of defects optic disc” Disease (screening function)  Definition of defects (e.g., location, shape, and depth)

 Clinical correlation (what caused the defect?)  The visual field defect tells you where the lesion is in the visual pathway  Knowing where the lesion is suggests what caused it

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Monocular limits of the visual field 7 8

Direction Limit Anatomy

Superior 60˚ Frontal orbit (brow)

Nasal 60˚ Nose

Inferior 70˚ Maxilla (cheek)

Temporal 110˚ Nasal retina

Binocular Overlap of Fields Traquair’s Island of Vision

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 The visual fields for the two eyes overlap allowing relatively large field defects to go unnoticed by the patient

 Because of this phenomenon, perimetry is ALWAYS performed MONOCULARLY

Factors influencing visual field measurements Factors influencing visual field measurements STIMULUS FACTORS

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 Luminance Stimulus Response  Contrast Factors Factors  Stimulus Size  Duration Clinical  Kinetic vs. Static Variables Presentation

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Factors influencing visual field measurements Factors influencing visual field measurements RESPONSE FACTORS CLINICAL VARIABLES 13 14

 Patient instructions  Pupil size  Patient’s expectations  It is best to test the visual field with a pupil diameter of  Examiner’s personality at least 3 mm (record pupil size when testing visual field)  Response criterion  The patient’s willingness to say “yes” when a target is  Fixation presented  Important to monitor during visual field testing  Strict criterion – higher threshold  Target blur decreased sensitivity  Relaxed criterion – lower threshold can result in an  Media opacities (e.g., cataracts)  Reaction time overall depression in  In general, the more peripheral the stimulus, the longer  Age the visual field the reaction time

Factors influencing visual field measurements CLINICAL VARIABLES 15

 Physical limitations  Psychological factors  Overhanging brow  Fatigue 16 Methods of visual field testing  Ptosis of upper lid  Anxiety/stress  Trial lens frame  Practice  Large nose  Attentiveness/Cooperation  Psychogenic/malingering

Confrontation Visual Fields Amsler Grid

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 Estimates the patient’s visual field limits as compared to the  Used by the patient to clinician’s field self-monitor changes in  Helpful in picking up the central 10° of the gross defects such as visual field hemianopsia, quadrantanopsia, or  Used in monitoring altitudinal loss macular disease  Typically part of the basic patient workup

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Manual Perimetry

 Tangent Screen  Goldmann Bowl 20 Automated Perimetry

Using an automated perimeter Humphrey Field Analyzer II (II-i)

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 Screening tests  Used for detection of a defect  Major advantage is speed of test  Disadvantages includes having limited data for quantification (not as accurate)

 Threshold tests  Allows for assessment of defects  Test takes longer than screening test  More accurate than screening test

Humphrey Field Analyzer III Humphrey Field Analyzer

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 Uses a bowl/perimeter with a radius of 33 cm  Because of working distance, presbyopia or cycloplegia will affect the clarity of the targets presented to the patient  Testing within the central 30˚ of the visual field should always be done with a nearpoint correction in place

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Perimetry Compensation Lenses Perimetry Compensation Lenses

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 The patient’s habitual nearpoint  The compensation lens correction is not suitable for can be manually perimetry because: determined and  It is set for a different distance entered into the HFA II (ie., 40cm vs. 33cm) (II-i), or you can have  It is usually in the form of a the the machine multifocal which would be useful determine the only for the inferior fields compensation lens for  Trial lenses used instead of glasses you (based on patient’s  Contact lenses should be removed distance Rx and date for testing, as tear film of birth) deficiencies and dryness can affect results of test

Perimetry Compensation Lenses Perimetry Compensation Lenses

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 The trial lens power you use depends on the  Absolute Presbyope (or cyclopleged patient) accommodative status of the patient:  Add +3.00 sphere to the distance correction  1. Absolute presbyope (or cyclopleged patient)  2. Intermediate presbyope  3. Non presbyope Example: Distance Rx: -1.75 -1.25 x 086 Trial Lens: +1.25 -1.25 x 086

Perimetry Compensation Lenses Perimetry Compensation Lenses

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 Intermediate Presbyope  Non-Presbyope  The rule-of-thumb is to add +0.50 sphere to their  Usually, you can use their customary distance Rx in the habitual add trial lens

Example: Example: Distance Rx: +2.75 -2.25 x 107 Distance Rx: -3.75 -1.50 x 172 Add: +1.25 Trial Lens: -3.75 -1.50 x 172

Trial Lens: +4.50 -2.25 x 107

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Perimetry Compensation Lenses Perimetry Compensation Lenses

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 Cylinder power  Select a trial lens that is  If the cylinder power is greater than 1.00D, correct all the least likely to block of the cylinder patient’s side vision

 If the cylinder power is 1.00D or less, use the  Trial lenses are only used Better choice! equivalent sphere when testing within the  If cylinder is used, place it in the lens well closest to the central 30˚ of vision patient’s eye  If not using a trial lens, holder can be stored behind chin rest

Example of trial lens artifact that Perimetry Compensation Lenses disappears after retesting 34 35  An improperly positioned trial lens will produce a ring scotoma  Using the wrong prescription can result in a central scotoma or depression of the visual field  The bottom line is:  Always ask the patient if their fixation target is clear before proceeding with the Keltner, J. L. et al. Arch Ophthalmol 2000;118:1187-1194.

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HFA III Preparing the Patient

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 No trial lenses needed!  1. Clean chin rest, forehead rest, response clicker, and eye patch with alcohol prep  “Liquid Lens”  2. Dim room illumination technology  3. Explain the purpose of the test and give patient  Automatically loads instructions patients correction  Explain what the test measures  Assure the patient that the test is painless based on data  Explain proper forehead and chin position entered  Explain where and how to fixate and how to respond Zeiss.com  Faster  Reinforce that attention to fixation and responses will speed the testing and improve accuracy  Less error  Tell them to inform you if they need to pause the test at any time

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Preparing the Patient Preparing the Patient

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 5. Hand the patient the response “clicker” and Incorrect Patch Position Correct Patch Position demonstrate its use  If the “clicker” is depressed for several seconds, it will pause the testing  6. Use the forehead and chin rest to position the tested eye as near as possible to the center of curvature of the bowl (and to the trial lens)  7. Direct the patient’s gaze to the fixation target  Foveal threshold will be checked first  8. Use the eye monitor and chinrest controls to center  4. Have the patient remove their eyewear and the eye patch the untested eye  9. Start the test

Main Menu Patterns of threshold testing

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 Central 30-2  ’30’ stands for central 30˚  ‘2’ stands for 2nd type (test points straddle the midline vs. 30-1 where points are on the midline)  76 points total are tested with each point separated by 6˚ of visual space

Humphrey 30-2 test pattern Humphrey 30-1 test pattern

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Patterns of threshold testing, cont. Patterns of screening testing

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 Central 24-2  C-76 Screener  Covers central 24˚ (except nasally where it extends out to 30˚) ; 54 points with 6˚ between points  Screens the central 30˚  Takes less time than Central 30-2  Uses exact test point pattern as the 30-2  Central 10-2  Full field 81/120  10˚ ; 68 points with 2˚ between points  Most often used on patients with conditions that affect  Custom central vision (ie., macular degeneration, diabetic retinopathy) or when only a small amount of central vision remains (ie, end-stage glaucoma)  Also useful as a screener for potentially toxic medications (ie, Plaquenil)

Patient Data Start Screen

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Parameter Setup Parameter Setup-Test Strategy

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 SITA=Swedish Interactive Thresholding Algorithm  The operating system for the HFA II  Questions and pace of test are determined by patient’s responses which helps reduce testing time  SITA Standard  Offers high accuracy in a relatively short test time  SITA Fast  Twice as fast (e.g., 3 min for 30-2 vs. 7 min for 30-2 on SITA Std)  Best used for “screening” or practice threshold tests

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Start Screen Reliability Indicators

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 Eye monitor used for  False Negative initial setup and to  A catch trial that indicates the patient is not responding confirm proper position to stimuli that were previously seen and fixation throughout  Likely indicates that the patient is becoming fatigued or the test is inattentive and should be re-instructed and encouraged  Reliability indicators  The pause control can be used to give the patient a rest  False negative  May also be high in a reliable patient with significant  Fixation losses field loss  False positives

Reliability Indicators Reliability Indicators

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 Fixation Losses  False Positives  When the test begins, the machine "locates" the blind  False positives are not shown on the SITA screen (you spot by an initialization process will need to monitor the decibel graph to catch high  During testing, presentations of stimuli are presented in false positives) the position of the blind spot, and a fixation loss is assumed if the patient responds  False positives are determined by using periods during the test when no positive answers are expected  Fixation losses are presented as a fraction with the numerator representing the number of losses and the (ie, “trigger happy”) denominator representing the number of presentations  Instruct the patient to respond only when a stimulus is seen and that he/she may not be able to see all of the stimuli  If a patient appears to have >33% fixation losses, it is probably worth it to pause the test and reinstruct the patient that are presented towards the fixation target

Decibel Graph Fixation Monitoring

54 55  The dB (decibel) numbers The following are used on the Humphrey Field unit are a measure of the patient’s ability to see dim to assist in monitoring fixation and in gauging stimuli patient reliability:  Range from 0 to 50  direct video observation of the patient’s eye  30 is fairly normal  blind spot stimulus presentations  0-20 indicates low sensitivity and significant  gaze tracking field loss  >40 indicates “hypersensitivity” and that the patient may be “trigger happy”—usually indicating an unreliable test

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Fixation Monitoring-Gaze Tracking

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Good fixation with a large number of blinks

Poor fixation with a large number of eye movements

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 Patient information  Reliability  Name Indices  DOB   Age Fixation Losses  Exam date/time  False Positives  Trial lens used  False Negatives  Pupil size   Best VA Fixation  Test Parameters Monitoring  Test pattern and  Gaze tracking strategy  Stimulus size and color

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 Threshold Sensitivity  Total Deviation  numeric values of the  The upper plot represents the sensitivity of each difference, in dB, between the point tested (in dB) numeric scale values and the age-corrected normal values  some points may be  The symbols beneath the plot retested and will show indicate the relative a value in parenthesis probability that the below the original corresponding deviations value occurred by chance alone  Grayscale  Pattern Deviation  Symbolic  The single most useful analysis representation of the on a HVF printout numeric scale  Similar to the Total Deviation  Used mainly for plot except it is adjusted for patient education— any changes in the height of the measured hill of vision. not for doctor’s This makes the analysis interpretation sensitive to any localized scotomas ‘hidden’ under an overall field depression

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Comparing Total and Pattern Deviation

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 Glaucoma Hemifield Test  Corresponding points above and below the horizontal midline are compared to determine if any deviation is outside normal limits  Global Indices  Mean Deviation (MD)  the mean elevation or depression of the patient’s overall field compared to the normal reference field  Pattern Standard Deviation (PSD)  measures the degree to which the patient’s field departs from the expected shape (smoothness of the hill of vision)

Global Indices Billing & Coding for Visual Fields

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 VFI – Visual Field  92081 Index  Limited examination  Included in HFA II-i  92082 and later software  Intermediate examination  Approximately 100%  92083 in normal fields and  Extended examination approaches 0% in  E.g., Humphrey visual field analyzer full threshold programs 30-2, 24-2 perimetrically blind fields  Clear documentation of the reason for testing including  With successive fields, corresponding ICD-10 code and interpretation of the can calculate rate of visual field in the patient’s record are required progression  VF codes are bilateral

OOPS!! Your responsibilities as a technician…

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 To be comfortable and knowledgeable with the  Common mistakes in administering the instrument used visual field test…..  To perform accurate and reliable visual fields  No patch – no blindspot and the periphery is unusually  To perform repeatable visual fields large  To accurately gather diagnostic data  Wrong trial lens Rx – generalized depression in central  To keep the patient as comfortable and relaxed as 30 degrees of visual field possible  Incorrect placement of trial lens – ring scotoma  To monitor the patient during testing  Patient fatigue – inconsistent responses, high false  Do not leave the patient unattended! negatives and fixation losses, superior visual field loss  Monitor fixation, attentiveness, positioning  Ptosis, dermatochalasis – superior visual field loss  Keep in mind, this is not a speed test!!